Coincidence-telemeter.



lo. EPPENSTBIN.' GOINCIDENGB TELEMETBR. i APPLICATION FILED JARA, 1909.

940,1 37. Pateted Nov. 16, 1909.

E soo soo mao am lwoo @D IIIIIIIII UNITED STATES lPATENT yOFFICE.

or'ro EPPENSTEIN; or JENA, GERMANY, AssIGNon 'io THE JENA, GERMANY.

MRM or CARL zmss, or"

ooINcIDiicE-T'ELEMETR.

Specification of Letters Patent.

Patented Nov. 16, 1909.

Application filed January 4, 1809. Serial N o. 470,595.

prehensive sense of the word. To these instruments belong all thosemonocular telemeters, of whose two image fields at least one extends inthe direction of the base line through the whole field of the ocular,and whose two images can be shifted relatively to one another in thedirection of the base line, in order that the difference in position ofthe two image points corresponding to an object point can be set to zeroin the direc- .tion of the base line, that is to say, coincidence forthese two points can' be produced, either in the literal or in themetaphorical sense. in some telemeters of this kind, a's is well known,the two image fields are superimposed, while in others they areseparated. Ordinarily the images are both completely erected, thougharrangements also are known in which one image is inverted in thedirection'at right angles to the base line.

The object of the invention is to render measurement with the abovetelemeters about as simple as with the stereoscopic telemeter with afixed scale. In the latter instrument there is no need for manipulatinga setting device of any kind. whatever in taking measurement, andreading off the said fixed scale follows the observation immediately,since this scale is arranged in the field of view of the telescope.

A new coincidence telemeter, which requires no micromctriral settingdevice and permits the distance of the observed object point being readofi' on a fixed scale in the field of' the ocular, can be based on thewell known coincidence telemeter in the following manner. Throughdispensing with the micrometrical setting device the problem in thefirst place arises how to evolve another means for effectingcoincidence, Now the two images become capable of being shiftedrelatively to one another in the direction of the base line in a verysim le mannerthe difference in position of t e two image pointsrelatively to the direction of the base line, which image pointscorrespond tol the )bject point under observation, can conse-v quentlybe nullified-if the two images' be given different magnifications,atleast in the direction of' the base line. If the instrument equippedin this manner be rotated in the sighting plane, both images novethroughthe. ocular field in the direction Vof theV base line, but withdifferentvelocities according to their magnifications.

lf the rotation of the instrument be given such a signification as todirection, that the image point in the less magnified image leads theway, the image point in the more magnified image will catch up to it ata certain definite place of the ocular field. At this place,- inoreexactly expressed in the straight line drawn at right angles to the baseline and including the two image points, coincidence of the pairs ofimage points of all objectppints takes place, which have the samedistance as the one under observation. To every other distance a dif;

ferent place of coincidence corresponds. Frein this fact a fixed scaleof the distances with strokes at right angles to the base line may bedrawn within the field of the ocular. Since the length of the scale canbe no linger than the diameter of the ocular eh., under certaincircumstances the accuravj ofthe reading or the range of measurement maybe too' small. This draw;

back obviated by dividing one of the two y image yfields into two parts,which follow one anl'ither in the direction at right angles to the baseline, either immediately, in the case of the superimposed image' fields,or, in the case of the separated ones, in such a. manner that the twoparts are on either side of the undivided image field. Two scales canthen be employed, since the image points of each one of the two imageparts` come into coincidence with the correspond` ing image points oftheundivided image. In order that, however, l,either scale may formasupplement to or extension of the other, the two image parts as toAtheir arrangement must suitably differ from one anether. There can be,for instance, a mere difference in position, the instrument being soadjusted that the two'image parts are displaced relatively to eachotheriin the direction of the base line. In that case the two Scaleshave' the-same direction@ A difference in magnification between bothimage parts may be also serviceable. One image part must have a strongerand the other a weaker magnification than the undivided image. flhescales then have opposite direction.

In the annexed drawing: Figure l is 'the ocular field of' a telemeterwith horizontal 4base line constructed according to the inventains theimage of lesser magnification projected by the right telescope objectivewith shorter focal length and the upper image field contains the imageof greater magnification projected by the left telescope objective withlonger focal length. In order to more clearly illustrate the case thetelemeter is adjusted in the unusual manner in which the two images donot have the saine common level but a difference in height by means ofwhich the same objects are visible in both images. The funnel. a1, a2 ofa steamer at an infinite distance is visible above the horizon of theWater, besides which there is also a Steamship b1, b2 at a distance of500 meters. The instrument is directed, so that the images al and a2ofthe object at an infi` nite distance coincide with their center linesin the o: stroke of the scale. As it happens, the object b1, b2 occupiessuch a position on the water, that the vertical plane, which correspondsin the object space to the o@ stroke of the image field of the lefttelescope, also passes through the center line of this object., Hence inthe upper image field the center line of b2 also coincides with the costroke. Vihereasin the lower image field, which belongs to the righttelescope, the center line of b1 is displaced by the distance d50" tothe left of the stroke. Now if the instrument be'rotated in the sighting.plane to the right, both images pass through the ocular fiel-d to theleft. After b has thus crossed the distance Z2, it coincides with 1:both center lines lie in the same perpendicular to the base line, whichis represented by the stroke 500 of the scale. The distance Z1 crossedby b1 is shorter in length by d500. than Z2. Since the length d500 is'the same as in the usual telemeters having in both image fields themagnification which here exists in the lower one, and since, morcover,the lengths and il are in the same proportion as the magniications ofthe upper and lower image, the distance 2 between right one.

the stroke 500 andthe eo stroke can be easily calculated.

In the instrument the ocular field of which is shown in Fig. 2 the imageof the upper telescope has the smaller magnification. ft is received inthe right image field, being supposedly reversed in the horizontaldirection.` This reversal has many advantages with regard to the form ofthe scale here chosen. The objects shown are the same as in example Fig.l. The operation is analogous to that of the instrument shown in ifig.l, the base line and the sighting plane, while horizontal in the 4formercase, being here vertical. Also by means of dots a second position ofthe instrument is indicated, which is attained, in measuring thedistance of the object b1, be, by a rotation of the instrument in thesighting plane, whereby the .images are caused to sink down through theocular field.

In Fig. 3 the middle image field contains the image of the uppertelescope, which, at the same time, is also that of the lesser 1nagnification. The second image, appertaining to the lower telescope and ofgreater magnification, is visible in the two lateral arts of the ocularfield. lBy means of a just ment, both lateral image parts are displacedrelatively to one another in a vertical direc tion, so that the lowerend of the left scale has the same value as the upper end of the Therange of measurement is not larger thanliri Figs. l and 2, but isdivided between both scales, since the difvference between the twomagnifications is about half as large as in those two examples. rtheimages are both completely erected. The instrument is adjusted, so thatin measuring coincidence (in the literal meaning of the word) oi theimage points takes place. 'ihe transfer from one scale to the otherrequ'ircs a lateral rotation of the instrument.

ln the ocular field according to Fig. i the image of the right telescopeoccupies the middle image field. The image-oi' the left telescope isvisible in the upper and lower image fields. 'l`he upper image part has.i lesser and the lower a greater magnification than the image in the`middle image field. By this means the two scales have oppositedirection. The funnelv in 'the upper field, having the leastmagnification, is denoted by a?.

' ln the instrument according to Figs. 5

.and (S the objectives are arranged behind the objective prisms c and d,on the r-iffht a com plete lens e2, on the left two half lenses, e1below and e above the axis ot' the instrument. rlhe focal length of c3is greater and that of cl less than the focal length of c?. Theseparating prism system consists of three prisms, ot' which the lower f"and the upper f3 are thicker than the middle one 'the three prisms arecemented together and,

by means of their back surfaces, also to a plano-parallel plate g. shownin Fig und the diaphragm of the ocular field, indicated by the boundarycircle in the saine ligure are arranged on the iont surf-.ice of theplete g. surface the innige projected by the objective lenses al, 2 andc3 are transferred by the separating prisms j, and f, A partition ilpreventa the rays which have passed through if* inteiniingling withthose which have pnf'sed through o, 5o that of the innige of the. lefttelescope the port with the greater inugnicution seen in the upper, thutwith the if.. ser in the lower innige li'ohl only. n

ocuhxr emnplees the optical equipment L ot' the instrument.

l clniin:

1. A ieleinoter consisting of two telescopes with one ocular. but euchhaving a lens: system which produces :i real object image extendingl`through rhe ocular field in the direction ot' the buse line, one of thelens systems having u greater focal length than The two scalesy Into thesaine the other, and a scale System fixed in the ocular held with thestrokes at right angles l to the hase line.

; i2. A telemeter consisting of two telescopes with one ocular, onetelescope having :L lens system which produces, a real-object l innigeextending through the ocular field in. 5 the direction of the haselinel` the other telescope having two lens systems of different, focallength, the focal length of one system lbeing larger and the focallength of the i other systeni Smaller than 'that of the lens l system ofthe first telescope und the partial syutems of the second telescopeextending direction of the bese line, and two supplel inentnry scales ofopposite direction fixed l in the ocular field side by side with the lStroltee et right angles to the hase line.

PA UL Kizorn,

i Vv'itnesses:

'FRITZ SAIQDER.

reel object images produced by the two lens side by side through theocular field in the

